This invention relates generally to a system and method for the conditioning of a dry milling stillage process stream with flocculant in order to facilitate further processing, separation, and recovery of solids, fats, and oils from the stillage. The dry milling process is a method of manufacturing ethanol. In this process, corn is ground up and processed to produce a “beer mash” which is fermented to form ethanol. Once the stream reaches the desired ethanol content the material it's then transferred to a stripper column. The stripper column facilitates recovery and removal of the ethanol and the remainder, known as whole stillage is passed on for further processing.
Whole stillage contains all of the non-fermentable components of the corn kernels including germ, protein, gluten, fiber as well as fats and oils and a small amount of starch in addition to dead yeast cells. Whole stillage typically contains 9%-14% totals solids of which 4% to 10% are suspended solids and 4% to 5% are dissolved solids. Many of the components of whole stillage are valuable and considerable attention has been paid in the industry to develop methods to separate and recover those components.
In prior art attempts such as U.S. Pat. Nos. 5,662,810, 5,958,233, 7,497,955, 7,566,469, 7,608,729, and 7,601,858 and US Published Patent Applications 2009/0259060, 2006/0041153, and 2008/0299632 describe various uses of heat and centrifuge pressures applied to whole stillage, thin stillage or syrup to recover at least some of these components. Typically prior art processes involve centrifuging away water from the whole stillage thereby forming concentrated solids wet cake and low solids thin stillage streams. The thin stillage then undergoes some form of drying or evaporation to form a viscous syrup. Part of the thin stillage stream may be reused in the process by recirculating to the front of the plant as backset and mixing it with new corn. The syrup is typically added to other solids recovered from the process to form a mass commonly known as distiller dry grains and solubles (DDGS), which can be used as an animal feed.
One constraint on these prior art recovery processes is the energy required for each separation step. Each step addresses ever-increasing proportion of solid materials or ever increasing viscosity of liquids. As a result significant energy, cost, and mechanical separation efforts are utilized to successfully separate these components.
Thus there is clear need and utility for improved methods, systems, and apparatus for conditioning whole, thin stillage concentrated thin stillage, and syrup. The art described in this section is not intended to constitute an admission that any patent, publication or other information referred to herein is “prior art” with respect to this invention, unless specifically designated as such. In addition, this section should not be construed to mean that a search has been made or that no other pertinent information as defined in 37 CFR §1.56(a) exists.